Germanium trifluoromethyl compounds

The state of the synthetic art in this area, in 1979, is much more satisfactory. During the past decade, several new synthetic developments have occurred such that we are closer to the point where the limitations upon synthesis of trifluoromethyl compounds are related more to stability problems in isolated cases, and are not nearly so much due to lack of widely applicable synthetic techniques. We find ourselves, for example, in a position in 1979 where the germanium compound, Ge(CF3)4, which in the past decade, was considered by many workers to be of insufficient stability to permit isolation, has been prepared by four independent methods and is known to be stable to over 100°C. Many of these new synthetic techniques have emerged from studies conducted in our laboratory at the University of Texas and previously... 

Attempted syntheses of trifluoromethyl derivatives of germanium, tin, and lead by thermal decarboxylation either resulted in decomposition of the trifluoroacetate without forming carbon dioxide (22,39,40) or gave carbon dioxide but no trifluoromethyl organometallic (22). In the latter case, the metal fluoride was detected. This suggests that the trifluoromethyl compound is thermally unstable and decomposes by fluoride abstraction. 

Tris(trifluoromethyl)germanium iodide is unstable in 3M base, however, and yields fluoroform quantitatively. All of the compounds showed good thermal stability (15). 

Bis(trifluoromethyl)mercury was found to react at elevated temperatures with both tin and germanium tetrahalides, resulting in a number of CF3-containing compounds including the fully substituted derivative of germanium, (CF3)4Ge Eq. (5)1. The reaction of tin tetrabromide with (CF3)2Hg, on the other hand, yielded only CF3SnBr3 and (CF3)2SnBr2, as shown in Eq. (6) (102). 

Of the bis(trifluoromethyl)cadmium derivatives obtained to date, the glyme adduct, (CF3)2Cd glyme, is the best compromise between chemical reactivity and thermal stability this compound appears to be almost a classic example of a lightly stabilized species, one which is stabilized enough to be isolatable but which is still quite reactive (107). That this material is a much more effective reagent than, for example, (CF3)2Cd 2 pyridine, can be most easily seen from the results of the reactions of these compounds with a second class of substrates, the halides of germanium and tin. Within 15 min at ambient temperature... 

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